Carburetor structure



Aug. 19, 1941. M. c. BROWN CARBURE'IOR STRUCTURE Filed March 29, 1940 INVENTOR MORRIS C. BROWN ATTORNEY UNITED STATES PATENT OFFICE CARBURETOR s'riwc'rmm Morris 0. Brown, Normandy, M0,, assignor to Carter Carburetor Company, St. Louis, Man, a corporation of Delaware Application March 29, 1940, Serial No. 326,645

6 Claims. (cl. 251-41 invention relates to, carburetors for internal combustion engines and more particularly resides in the provision of novel means for preventing "percolation of fuel from the main nozzle.

"Percolation or untimely exuding of fuel into the mixing conduit is caused by vapor pressures in the fuel passages, which become excessively heated due to their location, as in current downdraft carburetors, immediately above or adjacent the exhaust manifold. Means for relieving the pressures in these passages by providing vents 'and vapor bubble escape chambers have been disclosed as in the patent to James T. W; Moseley 2,013,787.

It is, however, ofutmost importance that the above mentioned vent to the main fuel passage be closed during those periods of operation wherein fuel is being supplied through the main fuel passage and main fuel nozzle to the mixing conduit. Otherwise, air-bleeding will occur, and although air-bleeding of the main fuel nozzle is practised, a vent properly located and proportioned so as to be effective in relieving pressures in the main fuel passage to prevent percolation,

could not practically be used reversely as an airnormal operating conditions, continues to discharge until the throttle valve is almost closed, it will be seen that the opening of the vent control valve must be accomplished by a comparatively slight angular movement of the throttle valve.

Anti-stall devices which have recently been incorporated in some carburetors function to open the throttle valve as the intake manifold suction drops below a predetermined point, these devices have the further purpose of presetting the throttle valve in order to facilitate re-starting of the engine. It will be seen from the foregoing that the incorporation of an anti-stall device of this character precludes the use of a throttle actu-' ated anti-percolating vent control valve which mustbe opened by a throttle closing movement at a time when the manifold vacuum becomes nil as when the engine becomes inoperative.

It is a primary object of the present invention to provide valve control means fora carburetor fuel passage vent which functions to close said vent when said main fuel passage is discharging and to open said vent when said carburetor is inoperative, irrespective of the position of the carburetor throttle valve.

Other objects and advantages will appear in the following description and accompanying drawing in which like numerals in the various figures refer to like parts. Referring to the drawing:

Fig. 1 is a somewhat diagrammatic view of a downdraft carburetor embodying one form of the present invention.

Fig. 2 is an enlarged detail of the control valve and valve housing, showing the valve in a closed position.

Numeral i indicates the main body member of a carburetor which is provided with a flange 2 at its lower end for attachment to the intake manifold 3 of an internal combustion engine. A mixture conduit 4 is formed through the main body casting l and an adjacent fuel chamber 5.

- choke valve l2 which is mountedfor rotation on ashaft I3. The, choke valve I2 may be operated'either manually or automatically. A throttle valve 14 mounted for rotation on a throttle shaft 15 is provided for control of the outlet 16 of the mixing conduit. An operating lever I1 is rigidly attached to the throttle shaft I5.

A substantially constant level of fuel is maintained in the fuel chamber 5 as indicated by the dot-dash line a:a:, by the action of the float l8 on'the intake needle valve 19. Fuel is supplied to the mixing conduit from the constant level fuel chamber 5 through the metering jet 20, through passages 2i and 22 and through the main discharge nozzle 23 from whence it is discharged into the primary Venturi tube 8.

ing of the metering orifice 20,1'a steppedand/or tapered metering rod 20a. is provided and arranged to be slidably positioned therein. The

branched, idling fuel supply, system comprising metering rod may either by positioned in accordance with the position of the throttle valve, by means of interconnecting linkage, or it may be positioned in accordance with intake manifold vacuum by a pressure responsive device, neither method being shown but both are well understood in the art. U

Rising vertically to the top of the, main body casting from the passage 22 is a comparatively large passage or chamber 3| which is threaded at its upper end to receive the threaded valve housing 32 and the threaded sealing plug 33. The valve housing 32 comprises a cylindrical, exteriorily screw threaded plug having a comparatively large longitudinal bore 34 extending upwardly through a greater portion of its length and in which is housed the ball valve 35; A valve seat 36 is formed near the upper end of bore 34 by the concentric reduced bore 31 which. completes a passageway through the plug. The upper end of the housing is provided with a screw driver slot 38 to facilitate assembly. The lower end of the plug is provided with several tangs 39 which are formed by slitting along the lines 40 and 40a and then bending inward to approximately a 90 angle to retain the ball valve 35.

i The ball valve 35 is preferably of light weight material as an aluminumalloy. The upper end of the passage/3| is connected to the mixing conduit at a point posterior to the throttle valve M by means of passages 4t, 42 and 43. The operation of the device is as follows:

During the operation of an engine to which the arburetor is attached, a sufiicient vacuum will exist in the intake manifold and in the mixing conduit posterior to the throttle valve to draw the ball valve 35 against the seat 36 as indicated '41 Fig. 2, thereby sealing the upper end of passag e 3|. When the engine becomes inoperative, the consequent loss of manifold vacuum permits the ball 35-to drop from itsseat thereby opening the upper end of passage 3!, whereby this passage is vented through the passages 36. 4|. 42 and 43.

The vertical passage 3| is madeconsiderably larger than the passage through nozzle 23 soas to provide a path of lesser resistance for vapor bubbles which may form near the base of the nozzle or anterior thereto. Further, the valve seat 36 is located at a point sufficiently above the fuel level a:a: to permit boiling or bursting/of these bubbles on the surface of the fuel in the passage 3|. This prevents the carrying of liquid fuel over through passages 31 and 4| by unbroken bubbles. It will be understood that the weight and diameter of ball 35 are so proportioned that the differential in pressures at a point below the ball valve in passage ,3] and in the mixing conduit below the throttle valve during all periods of engine operation will retain the ball valve 35 on its seat. The foregoing description and drawing are intended to be illustrative and "not limiting and the use of all modifications within the scope of the appended claims is contemplated.

I claim: W

1. In an internal combustion engine, a down- ,draft carburetor having a mixing conduit, a throttle valve for controlling the outlet of said mixing conduit, a constant level fuel chamber, a

fuel conduit system for conducting fuel from said fue chamber to said mixing conduit comprising a passageway extending diagonally upward'from a point near the bottom of said fuel chamber, a nozzle extending from the upper end of said passageway to a point in said mixing conduit slightly above the level of fuel, said nozzle forming a constricted continuation of said passageway, a branched passageway diverging from said diagonal passageway and rising substantially vertically to a point above the level of fuel and then downwardly and discharging near the upward opening edge of said throttle valve. a constant size atmospheric vent to said branched passageway at a point above the level of fuel, a second branched passageway substantially less restricting than said nozzle diverging from said diagonal passageway a d rising more directly to a point above the level of fuel, a passageway connecting the upper end of said second branched passageway with said mixing conduit at a point posterior ,to said throttle valve, and a gravity opened check valve positioned near the upper end and constructed and arranged to close said second branched passageway in response to suction consequentto normal engine operation.

2. A device as described in claim 1 in which said conduitsystem further comprises a highly restricted metering passageway, connecting said diagonal passageway with said fuel chamber.

3. In a carburetor, a downwardly directed mixture conduit, a constant level fuel chamber adjacent said conduit, a throttle valve in said conr duit located ubstantially below the level of fuel,

a nozzle opening into said conduit at a point above the level of fuel, ,a fuel passageway leading from said fuel chamber to said nozzle and being below the level of fuel, a vapor venting passageway'leading upwardly from said fuel passageway to a point above the level of fuel and then downwardly and opening into said mixture conduit at a point posterior to said throttle valve,

and a gravity opened check valve in said venting passageway at a point above the level of fuel and being subjected to the suction in said vapor venting passageway and being responsive with sufficient sensitiveness to said suction to close the vapor venting passageway at any degree of suction on which the carburetor would operate.

4. In an internal combustion engine, ,a carburetor having a mixing conduit, a throttle valve in said conduit, a constant level fuel chamber, a

- fuel conduit system for conducting fuel from said fuel chamber to a point in said mixing conduit above the level of fuel including a fuel passageway disposed below the level of fuel, a vapor venting passageway leading from said fuel passage way and opening into a[ zone of pressure which is atmospheric when the engine is not operating i and valve means controlling the venting passageway and being subjected to suction existing in the mixing conduit at all positions of the throttle .and being responsive with sufficient sensitiveness to said suction to close the venting passageway at any degree of suction on which the carburetor would operate.

5. In a carburetor, means forming a mixture conduit, a throttle valve in said conduit, a constant levelfuel chamber, )afuel conduit system for conducting fuel froin'saidiiuel chamber to said mixture conduit which includes a fuel passageway disposed belowthe level of fuel, a vapor venting passageway leading from said fuel passageway to said mixture conduit, and va lve means for controlling said venting passageway, said valve means being subjected to the suction insaid mixture conduit at all positions of said throttle and being sufficiently sensitive-to said suction to close said venting passageway at any degree of conduit. 7

6. In a downdraft carburetor, meanston nlng a,

chamber, a fuel conduit system'for conducting tueltrom the lower part of said fuel chamber toa point in said mixing conduit above the level of fuel including a fuel passageway'extendlng diagonally upward, a vapor venting passageway extending vertically from a. point in said diagonal mixture conduit, a throttle valve for controlling the outlet of said conduit, a constant level'mel Mir-I M ovvthe level, l ol yluel to a point Ithe level- 62' tuel'and'thejn downwardly and openlniflntould mlidnz conduit posterior to said throttlevalve; and a valve in geld ventlu: pu-

sajeewa'y 'l subjected to-the said ventinz newfiwi r n f eme waa v h sum l t sensitivenesje-to saldsuction to elosethe ventlng' passagewayi'at anydesree, of suction on which the carburetor'would operate. 10 I 

